Saturable optical absorber, and an application thereof to regenerating a wavelength division multiplexed signal

Abstract

A saturable optical absorber component is made of an inhomogeneous absorption material including a plurality of sets of quantum boxes formed in stacked layers. The sizes of the quantum boxes of each set define an absorption wavelength associated with the set.

What is claimed is:  
     
       1. A saturable optical absorber comprising: 
       an inhomogeneous absorption material comprising:  
       a plurality of sets of quantum boxes, wherein said sets are associated with respective different absorption wavelengths, said quantum boxes of a given set have dimensions chosen to obtain an absorption wavelength associated with said set, and said quantum boxes are disposed in a plurality of stacked layers;  
       wherein said absorber is adapted to enable an incident optical wave to pass through said stacked layers; and  
       two mirrors disposed on respective opposite sides of said stacked layers and parallel to or slightly inclined to said stacked layers.  
     
     
       2. The saturable optical absorber claimed in  claim 1  wherein each of said layers includes quantum boxes of the same set, layers belonging to different sets are stacked and form an individual absorption structure, and said absorber includes a stack comprising a plurality of individual absorption structures. 
     
     
       3. The saturable optical absorber claimed in  claim 1  including a stack comprising a plurality of layers each including quantum boxes of a plurality of sets. 
     
     
       4. The saturable optical absorber claimed in  claim 1  wherein the total number of layers of quantum boxes constituting said stacked layers is significantly greater than 80 if said mirrors have a reflectivity significantly less than 70% and significantly less than 80 if said mirrors have a reflectivity significantly greater than 70%. 
     
     
       5. The saturable optical absorber claimed in  claim 1  wherein said mirrors have a reflectivity substantially equal to 70% and the total number of layers of quantum boxes constituting said stacked layers is substantially equal to 80. 
     
     
       6. The saturable optical absorber claimed in  claim 1  wherein said saturable absorber material further comprises a wetting layer of a binary material followed by a layer of said stacked layers, this alternation of wetting layers and layers of quantum boxes being repeated, the combination being deposited on a substrate. 
     
     
       7. A method of using a saturable absorber to regenerate a wavelength division multiplexed signal, comprising: 
       providing a saturable optical absorber comprising:  
       an inhomogeneous absorption material comprising:  
       a plurality of sets of quantum boxes, wherein said sets are associated with respective different absorption wavelengths, said quantum boxes of a given set have dimensions chosen to obtain an absorption wavelength associated with said set, and said quantum boxes are disposed in a plurality of stacked layers; and  
       two mirrors disposed on respective opposite sides of said stacked layers and parallel to or slightly inclined to said stacked layers;  
       wherein said absorber is adapted to enable an incident optical wave to pass through said stacked layers; and  
       passing a wavelength division multiplexed signal through said absorber, wherein the absorber will substantially reduce noise present in the signal.